Field of the Invention
The present invention relates to a technique to acquire, in an image capturing apparatus provided with an image sensor capable of acquiring a captured image and phase difference information, the phase difference information for an object detected from the captured image.
Description of the Related Art
An image capturing apparatus is disclosed in Japanese Patent Laid-Open No. 2014-137567. The disclosed image capturing apparatus is provided with an image sensor including multiple image capturing pixels from which outputs for producing a captured image can be read out and multiple phase difference detection pixels from which outputs to be used for a focusing operation can be read out. Such an image capturing apparatus is desirable, in order to increase a focusing operation speed and improve an in-focus accuracy, that allows outputs from the image capturing pixels and the phase difference detection pixels to be simultaneously read out.
However, enabling such simultaneous readout of the outputs from the image capturing pixels and the phase difference detection pixels for a purpose of increasing resolution and frame rate significantly increases a number of terminals for reading out signals, which results in increase in size of the image sensor including the terminals. Furthermore, an increase in number of the phase difference detection pixels from which their outputs are read out causes a problem of increasing electric power consumption.
For such problems, as disclosed in Japanese Patent Laid-Open No. 2014-137567, a configuration may be employed that detects a specific object such as a face from the outputs from the image capturing pixels and read out the outputs from the phase difference detection pixels included in an area including the specific object in the captured image.
However, a large proportion of the specific object occupying in the captured image increases an area where the outputs of the phase difference detection pixels should be read out in the image sensor, and thereby the number of the phase difference detection pixels exceeds a maximum readable pixel number (pixel line numbers) in the image sensor. As a result, all the outputs of the phase difference detection pixels whose outputs should be read out cannot be read out, which makes it impossible to acquire required phase difference information.